The United States Supreme Court has struck down a key provision of the nation's campaign finance law. By a 5 to 4 vote, the justices eliminated the cap on the total amount donors can contribute in an election cycle. Until today, the aggregate limit was $123,000, but now donors will be able to give the maximum contribution to as many candidates and party committees as they want, an amount that could run in the millions.

NPR's legal affairs correspondent Nina Totenberg is just back from the court and joins us in the studio. Nina, good morning.

NINA TOTENBERG, BYLINE: Good morning.

GREENE: So could you start from the beginning? Give us a sense of what this case is all about.

TOTENBERG: Well, David, 40 years ago, in the aftermath of the Watergate scandal, Congress adopted a two-pillar system to limit the influence of wealthy donors in elections. In 2010, the Supreme Court struck down one pillar, which had limited what corporations and unions could spend on their own.

Now comes the other pillar - limits on contributions to candidates. And today, the court took away part but not all of that second pillar. It left intact the base limits on individual contributions to campaigns, which are currently $2600 for each election cycle. But it struck down the limit on the total amount that individuals can give.

So, where as previously under the law, you were capped at a total of $123,000 to all candidates, now you can give the base limit to as many candidates and party committees as you want.

GREENE: OK, so still limits on each individual candidate, but a person can give to as many candidates as they feel like in any election year. Well, the Chief Justice John Roberts wrote the opinion for the court. Give us a flavor of what he had to say.

TOTENBERG: Well, this is the second time that the conservative majority has struck down decades of campaign finance law. But this time, the chief justice sought to minimize the reversal, saying that 40 years ago when the court upheld the aggregate limits, it devoted only three sentences to it.

He acknowledged that the government has an interest in combating corruption. But campaign finance law, he said, must be aimed at regulating quid pro quo corruption and not any broader goal of limiting money in campaigns. It's true, he said, that many people would be happy to see fewer campaign commercials, but money and politics - and he said money and politics may at times seem repugnant to some people. But so too does much of what the First Amendment vigorously protects. And he said this: If the First Amendment protects flag-burning funeral protests and Nazi parades, which the court has said it does, it surely protects political campaign speech.

GREENE: But certainly some disagreement on the court. I mean, this was a 5-to-4 decision.

TOTENBERG: Yes. But I should say that Justice Clarence Thomas, who is one of the five, wrote separately to say that in his view, campaign contribution limits should be abolished entirely.

GREENE: Oh, so, he thought that people should be able to give as much as they want, but give as give as much as they want to any candidate.

TOTENBERG: Exactly.

GREENE: The court did not do that though.

TOTENBERG: No. It left the base contribution limits intact, though I have to say I would expect - and very soon - that there will be cases coming - being brought to challenge even the base limits.

GREENE: And there are four justices who believe that this entire pillar should remain intact. Justice Stephen Breyer, you know, spoke for the dissenters. What did he tell us?

TOTENBERG: He signaled the importance of this decision by taking the unusual step of summarizing his dissent orally from the bench this morning, which is very rarely done. If the court's 2010 decision opened the door to campaign corruption, he said, today's will open a flood gate. Together, these two decision eviscerate our nation's campaign finance laws, he said, whereas the limit on contributions for individual donors was $123,000 in toto, the number, he said, is now infinity.

First Amendment, he noted, is aimed at making sure that the marketplace of ideas is open to everyone, and whereas money calls the tune in the marketplace, the voice of the people will not be heard when it calls the tune, and a cynical public will lose interest in political participation altogether. And he said that democracy can't work unless people have faith in the system.

And joining him in the dissent where the court's three other liberals, Justices Ginsburg, Sotomayor and Kagan.

GREENE: All right, Nina, we know you'll be on ALL THINGS CONSIDERED, telling us more about this decision later on. NPR's legal affairs correspondent Nina Totenberg joining us in the studio. Nina, thanks a lot.